Investigators searching for the cause of a New York commuter train derailment that killed at least four people and injured more than 60 people said they will be looking at how fast the train was going when it crashed on a curve.

"The curve speed limit is 30 miles an hour. There is a 70-mile an hour zone just ahead of it, a 75 ahead of that," National Transportation Safety Board member Earl Weener said today.

The Metro-North passenger train was travelling from Poughkeepsie to Grand Central Station in New York City this morning when it derailed on a sharp curve in the Bronx borough of New York City, officials said.

Eleven people were in critical condition at area hospitals, according to New York Gov. Andrew Cuomo, although he said he believed they were in stable condition. Three of the dead were ejected from the train in the crash. Several people had to be extracted from the wreckage.

"We've always had this configuration. We didn't have accidents, right?" Cuomo said this evening. "So there has to be another factor and that's what we want to learn from the NTSB."

The train's operator was injured in the crash, but was expected to survive, Cuomo said. Investigators said they expect to interview the train's crew in the next few days.

The accident is the second passenger train derailment in six months for Metro-North and it marks the first time any passenger has died in Metro-North's nearly 31-year history. The train was estimated to have had around 150 passengers when it derailed.

"Obviously this is a very tragic situation," Cuomo said. "The first order of business is to care for the people on the train."

NTSB officials said they expected to be on the scene investigating for a week to 10 days.

The investigators would be looking at a host of factors to figure out the cause of the derailment, including the conditions of the track, the condition of the train, human error and signaling problems, Weener said.

"Our investigators will work on scene to gather factual information ... to document what happened and why it happened," Weener said.

Weener confirmed that the speed zone for the curved track was 30 miles per hour, while just ahead of that area it is 70 miles per hour. Event recorders from the train have been retrieved but not yet analyzed.

In July, a freight train also derailed near this same stretch of track, though not in exact spot. There were no fatalities in that crash.

The NTSB will look at the derailment of a freight train in July, which occurred along the same stretch of track, though not in the same spot, to see whether there was any connection with today's crash, but there was no immediate indication they were connected, Weener said.

The MTA will also work with the NTSB and might mafe procedural changes depending on the final NTSB report, Cuomo said.

"This is an opportunity to review the entire operation and all the procedures," the governor said. "Safety is job one and if there is a lesson to be learned from this tragedy we want to be sure we learn it."

The seven-car Hudson Line commuter train was headed toward Grand Central Station when it derailed near the Spuyten Duyvil Station in the Bronx on a long curved section of the track at around 7:20 a.m., according to Metro-North.

All seven cars of the train left the track.

Due to the damage the train suffered, FDNY Chief of Department Edward Kilduff said that airbags and jacks were used to stabilize the cars and remove victims. Some of those injured had to be cut out of the damaged train cars.

"The train is pretty beat up, it flipped to some degree," said Kilduff. "There was a lot of personal belongings thrown around."